Microcells for digital cellular telephone systems

Abstract

A cellular telephone system is described of the type wherein a plurality of contiguous cells, each having an assigned set of identification codes, are arranged with means for maintaining continuous communication with mobile telephones moving from cell to cell. The system allows multiple access by including means for assigning at least one of the in the assigned set of identification codes to more than one mobile telephone. A unique identification code is assigned to a mobile telephone located in the cell. A signal having a unique identification code is generated for identifying the mobile telephone. The signal is coupled to the zones. A combiner is also provided for combining signals from all of the zones in the cell. A receiver is coupled to the combiner for retrieving the signals having the code. According to another aspect of the invention, the signal coupled to the zones is delayed so that the transmission of the signal among the plurality of antenna sets is delayed by a preselected amount so as to reduce interference caused by successive reception of signals.

What is claimed is: 
     
       1. A cellular telephone system, comprising: (a) a plurality of cells, each of the cells being comprised of a plurality of zones, each of the cells having an assigned set of identification codes, and each of the identification codes being used to encode radio frequency (RF) signals communicated to a mobile telephone within the cell;   (b) at least one antenna suitably arranged and positioned within each zone and configured to limit propagation of radio frequency (RF) signals radiated therefrom to substantially within pre-defined boundaries of the zone;   (c) means, within each cell and coupled to the antenna, for transmitting and receiving the RF signals at assigned frequencies to communicate with mobile telephones within the zone, wherein a plurality of the mobile telephones simultaneously use an identical assigned frequency and a different one of the identification codes assigned to the cell;   (d) means, within each cell and coupled to the means for transmitting and receiving, for maintaining communications with the mobile telephones by activating and deactivating transmissions to the mobile telephones as they move from zone to zone while using the same identification codes for each of the mobile telephones; and   (e) means, within each cell and coupled to the means for transmitting and receiving, for maintaining communications with the mobile telephones by changing the identification codes for each of the mobile telephones as they move from cell to cell.   
     
     
       2. The cellular telephone system as set forth in claim 1 above, wherein the antenna is located on a periphery of the zone and is pointed into a center of the zone to substantially limit propagation of signals to the boundaries of the zone. 
     
     
       3. The cellular telephone system as set forth in claim 1 above, wherein the zones are arranged in a manner to create a substantially linear coverage for the cell. 
     
     
       4. The cellular telephone system as set forth in claim 1 above, further comprising: means for monitoring one or more characteristics of the RF signals received by the antenna from a mobile telephone; and   means for deactivating transmissions to the mobile telephone in all zones in a particular cell except for a zone in the cell selected on the basis of the monitored characteristic.   
     
     
       5. The cellular telephone system as set forth in claim 1 above, wherein transmissions of the RF signals to a particular mobile telephone in each of the zones of a particular cell occurs on the same assigned frequency, thereby eliminating handoffs between zones in the cell. 
     
     
       6. A cellular telephone system, comprising: (a) at least one cell, each of the cells being comprised of at least one zone;   (b) transceiver means, coupled to an antenna within a particular zone, for transmitting and receiving radio frequency (RF) signals at assigned frequencies to communicate with mobile telephones within the zone, wherein a plurality of the mobile telephones simultaneously use an identical assigned frequency, and wherein the antenna is suitably arranged and positioned within the zone and configured to limit propagation of the RF signals radiated therefrom to substantially within pre-defined boundaries of the zone;   (c) a base site, coupled to one or more of the zones via a communications link, for maintaining communication with the mobile telephones as they move from zone to zone, wherein the communications link further comprises first frequency conversion means at the base site for converting signals received at the base site from a cellular phone frequency to a first frequency, transmission means for transmitting the converted signals from the base site to the transceiver means in the zone via the link and for transmitting the signals from the transceiver means in the zone to the base site via the link, and second frequency conversion means at the zone for converting signals at the zone from the first frequency to the cellular phone frequency.   
     
     
       7. The cellular telephone system as set forth in claim 6 above, wherein the first frequency is a microwave frequency. 
     
     
       8. The cellular telephone system as set forth in claim 6 above, wherein the first frequency is an optical frequency. 
     
     
       9. The cellular telephone systems set forth in claim 6 above, wherein the first frequency is a baseband frequency.